The electrocardiographic (ECG) response to graded bicycle exercise (to 85% of predicted maximal heart rate) was evaluated prior to coronary angiography in 89 patients, aged 21 to 55 years, with type II hyperlipoproteinemia. We found that exercise electrocardiography results in a high frequency of both false negative responses (in patients with clinical suspected coronary disease) and false positive responses (in asymptomatic patients). We conclude that while exercise electrocardiography may be of value in epidemiologic studies, its applicability as a diagnostic tool in the individual patient has marked limitations.